A. Field of the Invention
This invention lies in the field of remote indicating and supervisory circuits and is concerned with a status indicating system for the instantaneous registration of the open or closed switch positions in a remotely controlled high tension plant. The high tension plant is provided with a large number of substations each having a group of high tension switches. Each high tension switch has two pilot indicating contacts for the respective switch positions. Pilot signals transmit information from the pilot indicating contacts to a central supervising station by a long distance transmission circuit to indicate, at the remotely located central supervising station, the positions of said two pilot indicating contacts, which positions are normally contrary. The supervisory circuit at said remote central supervising station also monitors contrarity of the pilot signals.
B. The Prior Art
The prior art which is used in commerce is described in FIG. 1 herein.
Status indicating systems of the type mentioned for high tension plants are known in which the two pilot indicating contacts are part of an auxiliary switch, which is mechanically connected to a movable part of the high tension switch to be supervised in such a way that one pilot indicating contact is closed and at all times the other pilot indicating contact is open. In view of the large number of high tension switches at a substation, which switches require supervision and for which interlocking tasks and functions are to be carried out, a multiplicity of further contacts is necessary and connecting leads are to be laid from the multiple contacts to a control switchboard at the substation, which leads cause considerable and expensive wiring requirements in the conventional status indicating system. Even more disadvantageous in the conventional status indicating system of the high tension plant is the fact that the status indicating system is not completely supervised for possible internal faults since it cannot be immediately determined from the central supervising station when that part of the status indicating system is defective, which belongs to a supervised high tension switch, which is just in off-position. Finally, with the conventional status indicating system it cannot be determined from the central supervising station whether a detected fault is caused in a substation or along the long distance transmission circuit, which often causes difficulty in locating the fault.